The Common Seen Plastics (Part One)

Plastics are widely used and there are many types. There are nearly a thousand pages just for The Handbook for the General Plastics. I hope this article can be helpful for everyone to know more about plastics.

1. PET

Main applications of PET
PET is mainly used for beverage bottles, screen protectors and other transparent protective films. PET can also be spun, which is what we often call polyester. During the Olympics, there was a saying that beverage bottles would be recycled to make clothing. Many sportswear pursuing breathability and lightness are made of polyester. The popular clothing material "dacron" a long time ago was also made of PET. However, the clothing made of dacron was not as comfortable to wear as it is now due to the backward spinning methods at that time. In addition, PET is also applied to engineering.
 
Using tips
PET is non-toxic, but the synthesis process may retain monomers, low molecular oligomers and side reaction products such as diethylene glycol. These are all toxic to a certain extent. There are strict national standards for PET used for beverage bottles.
 
PET has a high melting point in plastics. However, general bottles are not recommended to be reused, especially for boiling water. PET bottles are generally thin, they are manufactured by blow molding. When the bottle body is heated to about 90°C, it will be twisted and contracted due to the rearrangement of the PET molecular chain and internal stress. If you use it at this time, you will be easily burnt. In addition, high temperatures increase the risk of harmful substances leaching out from the material.
 

2. PE

Polyethylene includes high-density polyethylene (HDPE), low-density polyethylene (LDPE) and linear low-density polyethylene (LLDPE).

 
Main applications of PE
At present, PE is the most widely used plastic. PE can be used in all aspects of daily life by different modification methods. Plastic buckets, films, inner walls of paper cups, water pipes and cable sheaths are representative products of PE.
 
Using tips
PE is non-toxic. However, some processing or modification additives such as fillers, stabilizing additives or pigments are used in production. Some additives are toxic. PE products will soften or even melt at higher temperatures, using them over a temperature of 100°C should be avoided as much as possible.
 

3. PVC

Main applications of PVC
PVC is now mostly used to make some cheap artificial leather, foot pads and sewer pipes. It is widely used in the manufacture of wire and cable sheaths due to its good electrical properties and certain flame retardant properties. In addition, PVC is widely used in industrial fields, especially in places with high requirements for acid and alkali corrosion.
 
Using tips
A lot of plasticizers such as DOP and heat stabilizers containing heavy metals are used in the production of PVC, and it is difficult to eliminate the existence of free monomers in the synthesis process, which are considered to be toxic. Therefore, PVC is gradually being replaced by PP and PE in the application of human body contact, especially in medical and food applications. PVC is a kind of plastic which is not resistant to high temperatures and cannot be used in high-temperature places.
 

4. PP

Main applications of PP
PP has a wide application. It can be used for daily necessities such as packaging, toys, washbasins, buckets, hangers, water cups, bottles, etc. It can also be used for engineering applications such as car bumpers. PP spun into silk is called polypropylene, which is very common to be seen in textiles, non-woven fabrics, ropes, fishing nets and other products, and the take-out packaging boxes in the fast-paced take-out industry are also made of PP.
 
Using tips
PP and PE have similar processing methods and scope of use, and they are also non-toxic. The possible threat comes from the additives in processing and modification. Anti-aging agents containing heavy metals may be used in production, especially because of the poor heat resistance of PP. Compared with PE products, PP products have slightly better heat resistance. Typical LOCK&LOCK water cups can be used at a temperature of 110°C. There will be a danger of softening and melting if the temperature exceeds 110°C, which should be avoided.
 
5. PS
Main applications of PS
PS is mainly used for cheap transparent products, foam plastics, CD boxes, water cups, fast food boxes and insulation linings.
 
Using tips
The raw materials used to synthesize polystyrene are poisonous. Through a suitable synthesis process, the residual monomers of polystyrene are already very little, but this material is rarely used in water cups now. Polystyrene is flammable, especially PS after foaming. Burning will produce a lot of toxic gas. In some high-rise fire accidents, because the widely used PS foam board is used as the insulation material, a large amount of smoke and toxic gas generated after the fire have become the main cause of a lot of casualties.